Completion Design Study

iProdTech was contracted by a UK based operator to conduct a completion design study for a subsea gas condensate field development in the UKCS consisting of two subsea sub-horizontal wells. The work was undertaken during Q2/Q3 2017 and covered the following activities.

Lower completion design

The lower completion design included:

  • Management and interpretation of third party core testing studies including rock mechanics, sand control equipment and formation damage testing.

  • Geomechanics review to determine the requirement for sand control.

  • Sand control system selection and design.

iProdTech uses the standard workflow outlined in SPE 88493 for lower completion selection and design. This approach has been extensively utilised throughout this study. Based on the study, the recommended lower completion type selected was ‘Cased and Perforated Liner’ with drop and shoot tubing conveyed perforation (TCP) technique.

Further detailed design work during the equipment procurement phase has been recommended for further evaluation of horizontal oriented perforation gun systems, OBM drilling fluid design to ensure minimal formation damage, and developing a subsea well sand management plan.

Upper completion design

The upper completion design included:

  • Reservoir inflow performance modelling

  • Tubing size selection

  • Production chemistry review/completion metallurgy selection

  • Tubing stress analysis

  • Functional design specification

The analysis of the life of field well performance indicated that 4 ½” tubing is the preferred completion size for the development wells.A separate production chemistry study identified the risk of downhole calcium carbonate self-scaling and potential asphaltene deposition. A chemical injection mandrel has therefore been included in the basis of design. The chemical injection mandrel would also provide contingency to inject surfactants to mitigate liquid loading if required. Based on CO2 and H2S concentrations and considering the formation water properties and downhole temperature, 13 Cr has been recommended for the tubing metallurgy. Tubing stress analysis indicated that, for a 4 ½” completion, 12.6 ppf 13CrL80 tubing is sufficient to meet all of the anticipated load cases for the planned development wells.